1. Field of the Invention
This invention relates to a belt speed controller in a single facer for producing a single-faced corrugated board by nipping a corrugating medium and a liner between a lower fluted roll and an endless belt extended over a plurality of rolls so as to paste them together, in which a braking force is applied to the endless belt when the lower fluted roll is decelerated to prevent defective bonding between the corrugating medium and the liner to be caused by the difference in the speed of the lower fluted roll and that of the endless belt.
2. Description of the Related Art
In a system for forming a single-faced corrugated board (so-called single facer), an upper fluted roll and a lower fluted roll each having wavy flutes formed on the circumference are rotatably supported between frames in a vertical relationship in such a way that they may engage with each other by their flutes, and a press roll is designed to be brought into press contact with the lower fluted roll via a corrugating medium and a liner which are the webs of the single-faced corrugated board. Namely, the corrugating medium, which is fed between the upper fluted roll and the lower fluted roll, is allowed to have a predetermined corrugation (flutes) when it passes between these rolls. A starchy glue is applied to the crests of corrugation thus formed by a gluing roll provided in a gluing mechanism. Meanwhile, the liner being fed from the side opposite to the corrugating medium via the press roll is pressed against the glued crests of the corrugating medium between the press roll and the lower fluted roll to be pasted together and form a single-faced corrugated board.
The press roll employed in the conventional single facer is of a large-diameter metallic roll which is normally urged toward the lower fluted roll so as to apply a predetermined nip pressure to the corrugating medium and liner passing between these rolls. Since flutes consisting of continuous alternative repetition of crests and troughs are formed at a predetermined pitch on the circumference of the lower fluted roll, the rotation center of the lower fluted roll and that of the press roll shift slightly as the point of press contact therebetween shifts from the trough to the crest or vice versa. Thus, as the result that the rotation centers of these rolls make cyclic reciprocating motions to be closer to or farther from each other as they rotate, great vibration and big noise are generated during formation of the single-faced corrugated board, causing the working environment in the plant to be worsened considerably. Besides, since both the press roll and the lower fluted roll are made of rigid metallic materials, an impact is periodically applied to the press roll (so-called the hammer phenomenon) every time the crests of the lower fluted roll are abutted against the press roll. Accordingly, linear press marks corresponding to the pitch of the crests of the lower fluted roll are formed horizontally on the surface of the liner in the thus formed single-faced corrugated board, disadvantageously.
As a countermeasure for the problems described above, it is proposed to use an endless belt in place of the metallic press roll so as to nip the corrugating medium and the liner in cooperation with the lower fluted roll. More specifically, the endless belt, which is extended over a plurality of rolls to run freely, is disposed adjacent to the lower fluted roll, and the corrugating medium and the liner passing between the lower fluted roll and the endless belt are adapted to be nipped therebetween and pasted together by bringing the endless belt closer to the outer surface of the lower fluted roll. Thus, the use of the endless belt can prevent generation of great vibration and big noise and also formation of press marks on the single-faced corrugated board.
In a corrugating machine provided with such single facer, a corrugating medium and a liner to be fed to the single facer is spliced with the webs currently used, respectively, in accordance with an order change which occurs during operation of the machine, and the running speed of the single facet is decelerated to a predetermined level for such purpose. In such case, because of the inertia of the endless belt which is greater than that of the lower fluted roll, the endless belt cannot be decelerated correspondingly at the initial stage of decelerating the upper and lower fluted rolls to cause a difference to be generated between the speed of the endless belt and those of the fluted rolls over the zone where the corrugating medium and liner are nipped between the endless belt and the lower fluted roll. Namely, if a difference is generated between the speed of the lower fluted roll which is in contact with the corrugating medium and the endless belt which is in contact with the liner, the corrugating medium and the liner slip from each other with respect to the feeding direction.
This invention is proposed in view of the problems inherent in the prior art and to solve them in a suitable manner, and it is an objective of the invention to provide a belt speed controller in a single facer which can prevent generation of difference between the speed of the lower fluted roll and that of the endless belt during deceleration of the lower fluted roll and can constantly achieve excellent bonding between the corrugating medium and the liner.